Copper smelting involves two primary process steps: (1) smelting to produce copper matte, and (2) converting to produce copper metal. While smelting technology has changed dramatically in the last thirty years, converting has changed little since Messrs. Peirce and Smith developed the side blown converter in the early 1900's. Although the Peirce-Smith converter has proven its worth over time, its design does not lend itself well to compliance with the ever increasingly stringent environmental requirements that copper producers must meet. This is due primarily to processing liquid matte, slag and metal in multiple vessels, and transferring each from one vessel to another by use of ladles and overhead bridge cranes.
In the late 1970's, Kennecott Corporation began an investigation of alternatives to Peirce-Smith with copper converting, and one result of its efforts was U.S. Pat. No. 4,416,690. According to the process of this patent, solid matte particles are fed to a converting vessel with oxygen and flux in such a manner that the converting reaction is conducted autogenously and with the evolution of substantially undiluted sulfur dioxide gas (which can be captured and used in the production of elemental sulfur or sulfuric acid). This converting process eliminates the need for the transferring of liquid matte from the smelting furnace to the converting furnace, and the concomitant fugitive gas emissions. The process is known as solid matte oxygen converting.
Mitsubishi Materials Corporation teaches in U.S. Pat. No. 5,205,859 an apparatus and process for the continuous smelting of copper. In this process, copper concentrate is melted and oxidized in a smelting furnace to produce liquid matte and slag, and then both are transferred to a separating furnace in which one is separated from the other. The liquid matte is transferred to a converting furnace in which it is converted to blister copper, and the blister copper is then transferred to a plurality of anode furnaces for further fire refining. The transfer of product from one furnace to another is accomplished by a series of launders and since the entire process is continuous, balanced production and transfer must be maintained to keep the process operational.
While the Mitsubishi and various other processes known and in use today all produce copper, to one degree of efficiency or another, all are subject to improvement, particularly with respect to environmental efficiency. The reality of today is that not only must the copper producer be cost efficient, but it must also be environmentally efficient. Not surprisingly, a continued interest exists in the development of copper producing technology that accomplishes both these ends.